Method for producing single-oriented silicon steel sheets having high magnetic induction

ABSTRACT

Ingot steel for use in producing a single-oriented silicon steel sheet having a high magnetic induction, the steel being a silicon steel containing less than 0.085% C, 1-3.5% Si, up to 0.060% S, 0.02 to 0.945% acid-soluble Al and at least one element selected from the group consisting of 0.007 to 0.30% Se, 0.077 to 0.20% Te and the rest being Fe. The ingot steel is hot-rolled to form a steel sheet, the hot-rolled steel sheet is subjected to an annealing for precipitating AlN in a temperature range of 850* to 1,200*C when Si is present in an amount of from 1 to 2.5%, and at a temperature range of 960* to 1,200*C when Si is present in an amount of 2.5 to 4%, the annealing being for a time of 30 seconds to 30 minutes. The annealed sheet is cold-rolled to obtain a steel sheet of final thickness, the cold-rolling being at a reduction rate of 60 to 95% when there is a single cold-rolling step, and when there is a plurality of cold-rolling steps the final cold-rolling step is at a reduction rate of 60 to 95%. The final steel sheet has a B10 value of over 19,100 gauss.

Sakakura et al.

METHOD FOR PRODUCING SINGLE-ORIENTED SILICON STEEL SHEETS HAVING HIGH MAGNETIC INDUCTION [75] Inventors: Akira Sakakura; Satoru Taguchi;

Toshiya Wada; Kiyoshi Ueno; Takaaki Yamamoto, all of Kitakyushu, Japan [73] Assignee: Nippon Steel Corporation, Tokyo,

' Japan [22] Filed: Sept. 24, 1971 21 Appl. No.1 183,686

Related U.S. Application Data [63] Continuation-impart of Ser. No. 812,147, April 1,

1969, abandoned.

[30] Foreign Application Priority Data Apr. 24, 1968 Japan 43-21686 [52] U.S. Cl. ..148/111, 75/123 L, 148/31 .55

148/112 [51] Int. Cl. Hlf l/04 [58] Field of Search 1423/11], 31.55, 112, 110; 75/57, 123 L- [56] References Cited UNITED STATES PATENTS 2,913,361 ll/l959 Fitz..; 148/110 3,157,538 ll/1964 lmai et al 148/110 3,159,511 12/1964 Taguchi et al. 148/111 3,287,183 ll/l966 Taguchi et al. 148/111 7 3,333,993 8/1967 Kohler 148/111 '1... 3,853,641 [4 1 Dec. 10, 1974 3,540,948 11/1970 BenfOrd et al. 148/112 3,671,337 6/1972 Kumai et al. 3,700,506 /1972 Tanaka et al. 148/112 OTHER PUBLICATIONS Baeyertz, M.; Nonmetallic Inclusions in Steel; Cleveland, (ASM) 1947, pp. 72-73.

Lyman, T.; Metals Handbook; Cleveland, Ohio,

(ASM) 1948, pp. 450-451.

[ 5 7] ABSTRACT Ingot steel for use in producing a single-Oriented silicon steel sheet having a high magnetic induction, the

steel being a silicon steel containing less than 0.085%

C, 13.5% Si, up to 0.060% S, 0.02 to 0.945% acidsoluble Al and at least one element selected from the group consisting Of 0.007 to 0.30% Se, 0.077 to 0.20% Te and the rest being Fe. The ingot steel is hot-rolled to form a steel sheet, the hot-rolled steel sheet is subjected to an annealing for precipitating AlN in a temperature range of 850 to 1,200 C when Si is present in an amount of from 1 to 2.5%, and at a temperature range of 960 to 1,200C when Si is present in an amount of 2.5 to 4%, the annealing being for a time of seconds to 30 minutes. The annealed sheet is coldrolled to obtain a steel sheet Offinal thickness, the cold-rolling being at a reduction rate of to when there is a single cold-rolling step, and when there is a plurality of cold-rolling steps the final coldrolling step is at a reduction rate of 60 to 95%. The final steel sheet has a B value of over 19,100 gauss.

2 Claims, 2 Drawing Figures PATENTEL HEB] 0:974

Magnetic induction B(KG) SEEN 2 0f 2 FIG. 2

O.| 0.2 0.4 O-TIQO 2.0 40 7010 Core loss (Watts/kg) INVENTORS Akira Sakakura Saroru Taguch: Tqsgm as; BY l 'xaaki Yamamofo f 'mmJudL. LPm/L.

ATTORNEYS 1 t METHOD. FOR PRODUCING SINGLE-ORIENTED SILICON STEEL SHEETS HAVING HIGH MAGNETIC INDUCTION This application is a continuation-in-part of application Ser. No. 812,147, filed Apr. 1, 1969, now abandoned.

This invention relates to ingot steel and a method for producingfrom said ingot steel, single-oriented electromagnetic steel sheets having an. easy magnetization axis l in the rolling direction of the steel sheet.

Single-oriented steel sheets are used mostly as iron cores for transformers and other electric devices. Therefore their magnetic characteristics, excitation characteristics and core loss values must be favorable.

Recently, it has become an important problem to make the size of electric devices such as transformers small and for this purpose a reduction inthe weight of t e core is required. In general, in order to be able to reduce the weight of the core to be used for electric devices a portion of a steel. sheet, wherein the magnetic linduction is high, must be used. Thus, a steel sheet having favorable magnetization characteristics, that is, a ,steel sheet having high. B characteristics, is needed, and more particularly a greater importance is attached ltd a steel sheet having a high saturated magnetic induction 8,. Further, it should be understood that when using that portion of a steel sheet, wherein the'magnetic induction is high, the core loss value generally increases. However, as compared with a material having low B characteristics, a steel sheethaving high B characteristics has a muchlower core loss inthe region ofhigh magnetic induction, and-.moreover-the increase in the core loss is at a lower rate, as the magnetic induc? tion rises.

Putting all points above-mentioned together, it can be said that an improvement in designedmagnetic flux density whichis to be unavoidably expected as the ca pacity of electric devices increases, can first be realized by providing electromagnetic steel sheets having very high magnetic induction. v

The present invention has for its object the supply of products which can meet the requirements as abovementioned. That is, according to the-present'invention it is possible to produce electromagnetic steel sheets which are markedly superior to any conventional single-oriented silicon steel sheets with respect to the magnetic induction B in.the rolling direction, that is, steel sheets which have a magnetic induction above 19,100 gausses, andup to 20,100 gausses.

Heretofore, in conventional silicon steel sheets, the reduction in resistance and the deterioration of core loss values were, due to the lowcontent of Si..Apart therefrom, it was also not possible to obtain on an in- An object of the present invention is to provide a composition of ingot steel suited to the production of single-oriented silicon steel sheets having high magnetic induction.

Another object of the present invention is to provide a method for producing from said ingot steel singleoriented silicon steel sheets having high magnetic induction.

Other objects of the present invention will be made clear by the following explanation and attached drawing.

FIG. l'shows excitation characteristics of a typical product of the present invention and FIG. 2 shows core loss values of the product of the present invention respectively.

The present invention relates to a method for producing single-oriented silicon steel sheets having high magnetic induction, in which a normal steel material or silicon steel-material which contains C and Al as indis pensable elements. In addition thereto, a small amount of either Se or Te or both and/or S are added to the above-mentioned steel materials according to known steel-making methods, melting methods and casting methods used in normal industrial techniques. The

dustrial scale steel sheets having crystals with a so-' called {1 10} 1 00 orientation. Consequently singleoriented steel sheets could not be obtained atall and their high B, value could not be utilized. By the method of the present invention, therecan be manufactured on an industrial scale ideal single-oriented electromagnetic steel sheets having high magnetic induction, th'at is, high B value, and moreover 'havinga high B, value,

even when the Si content is low, by -producing secon dary recrystallizationgrains having very well selected {1 10} l00 -orientation, extending over a wide range of silicon content such asfrom 0 to 3. 5%.

thus-prepared steel material is hot-rolled and then subjected to an annealing process and cold-rolling process one time or more respectively to make the final gauge. The thus obtained product is decarburized and then subjected to a finalannealing to generate secondary recrystallization grains having {1l0} 100 -orientation in the steelmaterial. The present invention is particularly characterizedin that the final cold-rolling is carried out ata reduction rate of 60 to depending upon the Si content and one of the intermediate annealings after the hot-rolling or between a cold-rolling and a sequential cold-rolling step is carried out in such a temperature range that the y-transformation may occur at least in a part of the steel material. This temperature range is 850 to 1,200C. according to the Si content (hereinafter the said intermediate annealing is called a special intermediate annealing). These steps cause AlN of desirable size to precipitate, so that the magnetic induction in the rolling direction will reach above 19,100 gausses andmaximum of 20,100 gausses.

. as, for example, by an open-hearth furnace, an electric furnace or a converter or melted by such a known melting method as, for example, by a high frequency electric furnace or vacuum melting furnace. A'slab-like.

ingot obtained by a continuous casting method, which recently came into wide use, can also be used as a material in the present invention. The atmosphere in the case-of casting is usually air but may be'a vacuum or an inert gas as well.

As described above, the material in the present invention may be made by any steel-making, melting and casting'methods. But the composition of the material must satisfy the following conditions, irrespective of the methods for producing the same, that is, irrespec tive of what steel-making, melting and casting methods are used.

Se Te 0.007 to 0.300% 0.007 to 0.200%

Further, inthe present invention, the abovementioned composition can contain 0.003 to 0.060% S. It is necessary that C in the above-mentioned material should be present in an amount sufficient to produce a 'y-transformation at least in a part of the steel in response to the Si content. According to our experiences, C in a steel ingot must be at least 0.025% where Si is 3% but may be about 0.005% where Si is In regard to the added elements, the inventors have the following view. Generally, in the production of a single-oriented electromagnetic steel sheet, a selected direction will be obtained since a secondary recrystallization in the {1 100 direction occurs in the final annealing. However, in such case, the precipitate produced by the slight amount of added element, plays an important role. Such precipitate may be examplified by nitrides, sulfides and oxides. Such role has been considered to merely finely disperse and precipitate the precipitate so that the normalgrain growth will be inhibited and the secondary recrystallization will be accelerated. However, the present inventors have discovered that, besides the above-mentioned role of the precipitate, a part'of the precipitate which has been precipitated in strictly regulated direction in coexistence with AlN,

whereby a stabilized process for industrially producing single-oriented electromagnetic steel sheets having a high magnetic induction ought to be able to be carried out. However, as a practical matter, if secondary recrystal grains accurately arranged in one direction are to be obtained, the allowable ranges of the composition and treating conditions will become so narrow that industrial stability must be sacrificed.

The present inventors have disclosed in U.S. Pat. No. 3,287,183 that, when 0.005 to 0.050% S is added, a single-oriented silicon steel sheet having a high magnetic induction stabilized by the coexistence of the AlN and sulfide can be produced and have further confirmed that Se and Tev have the same effect as S. The utilization of Se and Te in a silicon steel is disclosed in U.S. Pat. No. 3,157,538 and others and the utilization of S is disclosed in U.S. Pat. No. 2,913,361. However, with only these silicon steels, the B characteristic of the product is less than 18,500 gausses and no single-oriented silicon steel sheet having such a high magnetic induction as the present invention can be obtained. The effects of Se and Te shall be described. Table 1 shows the relationship between the magnetic induction B and the elements S and Se of products obtained by hot-rolling each of 18 silicon steel ingots (made in an electric furnace) containing about 38% Si and about 0.029% Al so as to obtain a hot-rolled sheet of a thickness of 3 mm.,

first cold-rolling it at a reduction rate of 30%, then annealing it a l,l00C. for'5 minutes, then finally coldrolling it at a reduction rate of 85.7% so as to reach a final gauge of 0.30 mm., decarburizing it at 800C. and finally box-annealing it at 1,200c.

a specific directional relation with the matrix, further hasthe capacity for selectively growing only crystal grains in a specific direction, which strictly regulates the direction of the secondary recrystallized grains so that, as a result, a product with excellent B characteristics can be obtained It has been confirmed that Alnitride is very effective as a precipitate having such spe-,

As evident from this table, wherein the B characteristic values achieved according to the invention are outlined by a heavy line, in the case of no addition of S (S 0.003%), by adding about 0.090 to 0.300% Se in coexistence with AlN and with'S up to about 0.033, there can be obtained a product having a B characteristic of more than 19,100 gausses. Further, where S, Se and AlN coexist and when S is about 0.030%, most of the highest B characteristics can be obtained. That is to say, whenthere is no addition of Se (Se 0.003%), S has been limited so as to be in the range of 0.005 to 0.050% (sec U.S. Pat. No. 3,287,183). However, it has been found that, where AlN, S and Se coexist as in the present invention, by using 0.007 to 0.300% Se, the object of the present inventioncan be obtained, even- .the orderof 3%, Se in the range of about 0.090 to about 0.30% will give high B characteristics.

Further, in regard to the Al content, the following i fact has been found. Table 2 shows the relationship be Table 2 Al Secondary recrystal grain generation (generating (wt.%) rate in and B Characteristic (at a generating rate of 100%) S no addition It is found from this that, when Se is added, even for an Al content lower than in the case when only S is added, a product having a high B characteristic will be obtained.

However, when the Al content is less than 0.010%, even if the secondary recrystallization is perfect, the B characteristic will be low and, when it is more than 0.045%, the secondary crystallization will be imperfect. In either case, the object of the present invention cannot be achieved.

Table 3 shows the relationship between the magnetic induction B and S and Se of a productobtained by hotrolling each of 17 silicon steel ingots (made with an electric furnace). B values achieved according to the invention are outlined with a heavy line.'The steel contains about 1% Si and, about 0.035% Also as to be 2.0 mm. thick, and after hot-rolling, is continuously annealed in N at l,050C. for 2 minutes, then cold-rolled once at a reduction rate of 82.5% so as to reach a final gauge of a thickness of 0.35 mm., then decarburized (continuously annealing) at 800C. and finally annealed in H at 950C. for 10 hours.

From the results of many experiments including these results, the present inventors have reached the following conclusion. That isto say, when using a low Si material having less than 2.5% Si, even by the precipitation of only AlN, there will be obtained a' product having a B characteristic of more than. 18,500 gausses. However, when less than 0.300% Se is added thereto or less than 0.60% S is' further simultaneously added thereto, there will be obtained a particularly excellent single-oriented electromagnetic steel sheet having a high magnetic induction. This has been found togive the same effect as when using a high Si material having 2.5 to 3.5 Si. Further, the Al content in the steel ingot required to precipitate desirable AlN is 0.02 to 0.045%.

It has also been found that Te in a range of 0.007 to 0.200% has the same effect as Se. As shown by theexamples, there has been obtained a product having a B characteristic exceeding 19,100 gausses by having AlN coexist with Te (0.007 to 0.200%), AlN coexist with Se 1 (0.007 to 0.300%) and Te (0.007 to 0.200%), AlN coexist with S (0.003 to 0.060%), Se (0.007 to 0.300%) and Te (0.007 to 0.200%) or AlN coexist with Te (0.007 to 0.200%) and S (0.003 to 0.60%).

In the above, the effects of the coexistence of the three elements S, Se and Te with AlN in the present in-.

vention has been described. As described above, the precipitate produced by the addition of these elements coexists with AlN and plays a role in inhibiting the normal grain growth and accelerating the secondary recrystallization in the final annealing. Therefore, even in the present invention, in a step before the final annealing such as, for example, in the intermediate annealing or hot-rolling step, or at the time of heating it, or at the time of elevating the temperature in the final annealing, these elements may be made to diffuse into the steel sheet so as to be contained in fixed amounts.

It is reported, for example, in U.S. Pat. Nos.

3,333,991, 3,333,992 and 3,333,993 that S andSe can be rather easily made to diffuse into steel sheets.

in the present invention, too, needless to say, those methods can be used.

C is adjusted so as to be present in an amount below 0.080% so that a -y-transformation will occur in at least a part of the steel sheet due to the Si content while carrying out a special intermediate annealing.

That is to say, the summary is as shown in the followmg: i

For less than 1% Si, less than 0.080%C is used (a steel ingot of less than 0.085% C).

.For 1 to 2.5% Si,'0.0l0to 0.080% C is used (a steel ingot of 0.015 to 0.085% C). t

For 2.5 to 3.5% Si, 0.020 to 0.080% C is employed (a steel ingot of 0.025 to 0.085% C).

The C in the steel ingot is 0.005% higher than before the steel sheet is important in carrying out the special intermediate annealing.

In case the content exceeds the upper limit of the above-mentioned specified range, the generation of secondary recrystal grains will become imperfect. On the other hand, when the C content becomes high, even if secondary recrystal grains are obtained, thesharpness of the secondary recrystallization texture becomes low and the product which is the object of the present invention can not be obtained.

, Si ispresent in an amount less than 3.5%. The present invention has an object to improve the B characteristic and B, characteristic. Therefore, the lower limit is not defined. But, as regards the upper limit, if Si is present in an amount greater than 3.5%,. the industrial coldrolling to produce the very high B value becomes impossible. i

The basis for generating secondary recrystal grains having a particularly excellent orientation of, the present invention is the formation of AlN. Therefore, in the present invention, the presence of any nitride other than that of Al and the nitride-forming elements must be noted in relation to the formation of AlN. As described above, the presence of the nitride contributes to the secondary recrystallization in the sense of inhibadd nitrogen in theannealing. The method of adding nitrogen is not critical but, in the present invention, it

iting the normal grain growth and the presence of the nitride-forming element is significant. However, this should bedetermined in relation to AlN. That is to say, it is necessary that Zr and Ti which are elements stronger than Al in their affinity for N should be added depending on the amount of N contained in the steel by taking into consideration that AlN can be precipitated in a specified amount after the annealing as described later. B, Ta, Nb, V, Cr, Mn, W and Mo are weaker than Al in their affinity for N and therefore may well be added in proper amounts already known in the production of single-oriented silicon steel sheets. The allowable maximum values of the amounts of these elements are shown to be 1% for V, Mn and M0, 0.5% for W and 0.1% for B, Zr, Ti, Nb, Ta and Cr. However, these are all only examples. It is not a deviation from the idea of the present invention to add elements in order to'produce precipitates for the acceleration of the secondary recrystallization within a range which does not obstruct formation of AlN. v

A material which has a composition conforming to the above-mentioned composition is made into product sheet thickness by at least one cold-rolling step. In such case, it is one of the features of the present application that the annealing after the hot-rolling or at least one intermediate annealing between the cold-rollings is carried out in a high temperature range in which a y-transformation will occur in a part of the steel sheet so that a desirable size of AlN may be precipitated. This annealing temperature is in the range of 750 to 1,200C. in which a 'y-transformation will occur in response to the Si content.

It maybe summed up as follows:

750 to 1,200C. for less than 1% Si.

850 to 1,200C. for l to 2.5% Si.

960 to 1,200C. for 2.5 to 3.5% Si.

is recommended that the annealing be carried out in a neutral or reductive gas containing at least 10% N byvolume. The above-mentioned special intermediate annealing may be carried out at any time during the period after the hot-rolling until the final cold-rolling,' and the time is not critical so long as it is in this period.

In the present invention, the cold-rolling is carried out one or more times and the final cold-rolling step may be carried out at a reduction rate of 60 to 95%, depending on the Si content so that the higher the Si content, the higher the reduction rate may be. It is not necessary to have any specific reduction rate in any other cold-rolling step. This can be said to be due to the effect of the coexistence of AlN, Se, Te and S in the material.

Any other intermediate annealing than the abovementioned special intermediate annealing at a specified high temperature may be carried out at a temperature and for a time which are sufficient to make the coldrolled structure a primary recrystal structure and are not critical. In the present invention, the number of times the cold-rolling step is repeated may be determined by the thickness of the hot-rolled sheet and the specified final cold-rolling reduction rate.

For example, when making a product 0.35 mm. thick from a hot-rolled sheet of Ho 2.5% Si, if the thickness of the hot-rolled sheet is 1.4 to 3.5 mm., it is possible to treat the sheet by'one strong cold-rolling process,

, after the AlN-precipitating annealing has been applied The annealing time in this temperature range is 30 seconds to 30 minutes.

When this annealing exceeds 30 minutes, the growth of crystal grainswill occur during the annealing and the development of the secondary recrystal grains in the final annealing will become imperfect. Further, this annealing may be a box-annealing but generally it is industrially advantageous to carry it out by a continuous annealing. With an annealing for less than 30 seconds, the sought for effect can not be obtained. The annealing atmosphere is related to the precipitation of AlN required for the secondary recrystallization as already described. Usually the steel ingot obtained from an open-hearth furnace contains, without any additions, more than 0.0040% N which is sufficient to precipitate the required AlN. Therefore, so long-as no remarkable denitrification occurs, the annealing atmosphere may be a reductive or neutral atmosphere such as, for example, of H Ar, a gaseous mixture thereof or air. However, if the ingot is obtained by vacuum melting or the like, there ,will be so little N that it will .be necessary to to the hot-rolled sheet. However,-if the thickness is 3.5

mm., the sheet is treated in two cold-rolling steps. F-urther, if the hot-rolled sheet is thicker, it can be coldrolled more than three times. However, from the industrial technical viewpoint, the hot-rolled sheet is usually 1.5 to 7 mm. thick.

The steel sheet of a product sheet thickness after the final cold-rolling is then subjected to a decarburi-zing annealing. This annealing is to make the cold-rolled structure a primary recrystal structure and at the same time to remove C which is detrimental when developing secondary recrystal grains in the {l10} l00 direction in the final annealing. Any known process may be used for this step.

The final annealing should be carried out at such a temperature and for such a time that secondary recrystal grains in the {110} direction can develop well. It is preferable to develop the secondary recrystal grains in a temperature range wherein no y-transformation is produced in response to the Si content and at a temperature as high as industrially possible, because the generation of 'y-transformation will change .the once obtained secondary recrystal grains in. the {l10} 100 direction so that they are in another direction. When Si is present in an amount less than 1%, it should be carried out at 950C. or usually at a temperature lower than that. However, the higher the Si content, the higher the temperature can be elevated.

When Si is present in an amount more than 2%, a temperature higher than 1,000C. is possible. On the other hand; below 800C, no. secondary recrystallization will occur. Unless the temperature is made high,

a product which has an excellent iron loss value can not for the generation of secondary recrystal grains if it is more than 1 hour but more than 5 hours is necessary in order to obtain a product having a low iron loss value with a high Si content. Further, no matter, whether the atmosphere is neutral, reductive or so weakly oxidative that the steel sheet will not be greatly oxidized, a product having a B characteristic of more than 19,100 gausses according to the present invention can be obtained. However, in order to obtain a low iron loss value with a high Si content,- it is preferable to carry out the annealing in H However, the description of such time and atmosphere has nothing to do with the substance of the present invention.

After Se, Te and S contained in the steel sheet have served for the development of secondary recrystal grains in the {l10} 001 direction in the finishingannealing by theircoexistence with AlN, they are so detrimental to the magnetic property or particularly to the iron loss that it is necessary to remove them or reduce the amount thereof as much as possible. It is known to improve the free-cutting property by including Se or Te 1 in a magnetic steel sheet product. However, the presence of such a large amount of Se or Te in the-product is very disadvantageous to imparting required excellent magnetic characteristics to the product. Therefore, after it has served for the development of secondary recrystal grains, it must be removed to a great a degree as possible. In order to remove Se, Te or S, the product may be annealed for a long time in H Particularly, if more than 1.2% Si is present, Se, Te or S can be removed by annealing at a temperature of above 1,000C. In order to attain the object of the present invention, it may be reduced to an amount less than 0.05%. Particularly, if it is reduced to an amount less than 0.01%, a favorable result can be obtained.

EXAMPLE 1 An Al-killed steel ingot containing 0.020% C, 0.041% A1, 0.024% S and 0.010% Se was bloomed and hot-rolled to a hot-rolled sheet 2.2 mm. thick. The content of C in the hot-rolled steel sheet was 0.017%. After EXAMPLE 2 A silicon steel ingot (prepared in an electric furnace) containing 0.030% C, 1.05% Si. 0.065% Se and 0.025% Al was bloomed and hotrolled to a'hot-rolled steel sheet 2.0 mm. thick. Afterthis hot-ro1led steel sheet was annealed in N at 950C. for 2 minutes, it was pickled and cold-rolled to make the thickness of the sheet 0.50 mm. (at a reduction rate of 75%). Then, the coldrolled steel sheet was decarburized by an open-coilsystem in a wet H at 750C. for -5 hours and thereupon fi- EXAMPLE 3 A silicon steel ingot containing 0.043%C, 2.15% Si, 0.010% S, 0.07% Se and 0.030% Al was bloomed and hot-rolled to a hot-rolled steel sheet 3.0 mm. thick. The C content of the hot-rolled steel sheet was 0.041% and was only slightly decarburized. This hot-rolled steel sheet was first cold-rolled by 30% to make the thickness of the sheet 2.] mm. and then annealed in N at 1,100C. for 2 minutes and thereafter pickled and coldrolled to make the thickness of the sheet 0.35 mm. (at a reduction rate of 83.3%). The thus cold-rolled steel sheet was decarburized in a wet H at 800C. for 3 minutes and then subjected to a final annealing, simultaneously attended with the desulfurization and deseleniumization. The magnetic characteristics in the rolling direction of the product were as shown in FIG. 1(C), that is,

B 19,750 gausses W 1.15 watts/kg.

In the composition of the final product C 'was 0.005%, Se 0.005% and 5 0.003%.

EXAMPLE 4 A silicon steel ingot containing 0.055% C, 2.95% Si, 0.025% S, 0.053% Se and 0.025% Al was bloomed and hot-rolled to a hot-rolled steel sheet 2.8 mm. thick. The

C content of the hot-rolled steel sheet was 0.051%. The" steel sheet was cold-rolled by 30% and then subjected to a continuous annealing in N at 1-,l50C. for 2 minutes. Then, the cold-rolled steel sheet was pickled and then again cold-rolled to make the thickness of the sheet 0.35 mm. (at a reduction rate of.82.1%). After the cold-rolled steel sheet was then decarburized in a wet H at 800C. for 3 minutes, it was subjected to a final annealing at 1,200C. for 20 hours, simultaneously attended with a desulfurization-and deseleniumization.

EXAMPLE 5 A silicon steel ingot containing 0.075% C, 3.09% Si, 0.025% 5,0030% Te and 0.060% Al was bloomed and hot-rolled to a hot-rolled steel sheet 3.2 mm thick. The C content of the hot-rolled steel sheet was 0.071%. The thus obtained hot-rolled steel sheet'was first cold-rolled by 20% to a thickness of 2.56 mm. After the cold-rolled steel sheet was continuo'uslyannealed in N at 1,150C.

nally annealed in H at 950C. for 10 hours. The prod-' uct had magnetic characteristics in the rolling direction A as shown in FIG. 1(B), that is,

B 19,730 gausses W 2.50 watts /kg.

for 2. minutes, it was pickled and again coldrol1ed to make the thickness of the steel sheet 0.30 mm. (at a reduction rate of 88.3%). Then, the thus cold-rolled steel. sheet was decarburized in wet H at 850C. for 2 min- In the composition of the product C was 0.004%,8

0.003% and Te 0.008%.

was 0.003%,

EXAMPLE 6 A silicon steel ingot containing 0.050% C, 3.12% Si,

' 0.041% A1, 0.030% S, 0.050% Se and 0.030% Te was hot-rolled to a hot-rolled steel sheet 3 mm. thick. After the hot-rolled steel sheet was continuously annealed at 1,100C. for 2 minutes, it was cold-rolled by 50%. Then, the cold-rolled steel sheet was annealed for a primary recrystallization at 900C. for 1 minute and coldrolled at a reduction rate of 84.7% to make the thickness of the sheet 0.23 mm. After the decarburization annealing, the steel sheet was subjected to a finishing annealing at 1,200C. for hours, simultaneously attended with a deseleniumization, detellerium ization and desulfurization.

The magnetic characteristics of the product were as follows:

B 19,250 gausses WIS/5o 0.71 watts/kg.

1n the composition of the product C was 0.003%, S 0.003% and the sume of Se and Te 0.008%.

What is claimed is:

l. A process for producing a single-oriented silicon steel sheet having a magnetic induction value above 19,100 gauss consisting essentially of:

a. hot-rolling a silicon steel ingot consisting essentially of 0.015% to 0.085% C, 145% Si, with the proviso that when Si is present in an amount of l2.5%, C is present between 0.015% and 0.085% and when Si is present in an amount of 2.53.5%, C is present in an amount between 0.025% and 0.085%; S in an amount up to 0.060%, 0.02 to 0.045% acid soluble Al, and at least one element selected from the group consisting of 0.007 to 0.30% Se and 0.007 to 0.20% Te, more than about 0.004% N and the rest being Fe to produce a hotrolled steel sheet; b. annealing the hot-rolled steel sheet to precipitate AIN at a temperature range of 850 to 1,200C I when Si is present in an amount of from 1 to 2.5%, and at a temperature range of 960 to 1,200C when Si is present in an amount of from 2.5 to 3.5%, the annealing being carried out for a time of 30 seconds to 30 minutes and c. cold-rolling the thus-annealed steel sheet to obtain a steel sheet of final thickness, the cold-rolling being effected at a reduction rate of 60%.to when there is a single coldwrolling step and when there is a plurality of cold-rolling steps, the final cold-rolling step being carried out at a reduction rate of 60 to 95%. 2. The method claimed in claim 1 in which the silicon steel sheet contains 0.007 to 0.30% Se and 0.007 to 0.20% Te. 

1. A PROCESS FOR PRODUCING A SINGLE-ORIENTED SILICON STEEL SHEET HAVING A MAGNETIC INDUCTION VALUE ABOVE 19,100 GAUSS CONSISTING ESSENTIALLY OF: A. HOT-ROLLING A SILICON STEEL INGOT CONSISTING ESSENTIALLY OF 0.015% TO 0.085% C, 1-3.5% SI, WITH THE PROVISO THAT 06 WHEN SI IS PRESENT IN AN AMOUNT OF 1-2.5% C IS PRESENT BETWEEN 0.015% AND 0.085% AND WHEN SI IS PRESENT IN AN AMOUNT OF 2.5-3.5%, C IS PRESENT IN AN AMOUNT BETWEEN 0.025% AND 0.085%; S IN AN AMOUNT UP TO 0.060%, 0.02 TO 0.045% ACID SOLUBLE AL, AND AT LEAST ONE ELEMENT SELECTED FROM THE GROUP CONSISTING OF 0.007 TO 0.30% SE AND 0.007 TO 0.20% TE, MORE THAN ABOUT 0.004% N AND THE REST BEING FE TO PRODUCE A HOT-ROLLED STEEL SHEET; B. ANNEALING THE HOT-ROLLED STEEL SHEET TO PRECIPITATE AIN AT A TEMPERATURE RANGE OF 850* TO 1,200*C WHEN SI IS PRESENT IN AN AMOUNT OF FROM 1 TO 2.5%, AND AT A TEMPERATURE RANGE OF 960* TO 1,200*C WHEN SI IS PRESENT IN AN AMOUNT OF FROM 2.5 TO 3.5%, THE ANNEALING BEING CARRIED OUT FOR A TIME OF 30 SECONDS TO 30 MINUTES AND C. COLD-ROLLING THE THUS-ANNEALED STEEL SHEET TO OBTAIN A STEEL SHEET OF FINAL THICKNESS, THE COLD-ROLLING BEING EFFECTED AT A REDUCTION RATE OF 60% TO 95% WHEN THEREIN IS A SINGLE COLD-ROLLING STEP AND WHEN THERE IS A PLURALITY OF COLDROLLING STEPS, THE FINAL COLD-ROLLING STEP BEING CARRIED OUT AT A REDUCTION RATE OF 60 TO 95%.
 2. The method claimed in claim 1 in which the silicon steel sheet contains 0.007 to 0.30% Se and 0.007 to 0.20% Te. 